The concerns you have expressed about NFP are valid, but I think they are exacerbated by your particular situation. I admire the love and respect you clearly have for your wife. From what you have written, however, it doesn't seem that she treats you respectfully. A husband should not have to "earn" sex with his wife. I understand the difficulties of low desire and irritability during Phase III, as I have been diagnosed with Pre-menstrual Dysphoric Disorder (PMDD) which makes NFP more difficult to practice. I was interested in sex during my fertile phase, but before I entered Phase III I became irritable, moody, and depressed. My energy level was very low during this time. Not understanding what was happening to me, I attributed my moods to a lack of loving attention ("romance," if you will) from my husband. His angry responses to my criticisms reinforced my ideas that he was to blame for my depressed mood. By the time my menstrual period was over, our resentment of each other often prevented us from taking advantage of a brief infertile time. Also, I suffered frequently from minor illnesses which interfered with sexual intimacy. Curiously, all of these problems existed before we began practicing NFP. NFP resulted in a great improvement in our marriage, but my own problems worsened significantly after the birth of our third child.
Since I have started taking antidepressant medication, I have been amazed at what a wonderful husband I have! While I still experience irritability during Phase III, my feelings are not so intense that they spill over into my relationships with my husband and children. I am able to experience joy and appreciation for the many blessings in my life. My energy level is higher, and my overall health is greatly improved. I have developed a fulfilling hobby and becoming more outgoing socially. These changes have positively affected our marriage. Although the particular medication I take has decreased my sex drive, my husband and I have sex more frequently than we did before I began treatment. More important is the improvement in my ability to convey to my husband the respect that he deserves. You also deserve this respect, and I hope your wife can address whatever issues are keeping her from honoring your needs. I do not know whether your wife is depressed, but Christian marriage counseling may be very helpful for both of you. I wish you and your wife all the best that marriage has to offer.